A known method of selecting a cell and a channel during a link setup for a call in a cellular communication system involves the use of a control channel that has a common inbound and a common outbound frequency for all cells and all cellular units operating in the communication system. When a link is to be set up, a mobile or portable cellular unit transmits a signal using the inbound control channel frequency, and the signal is measured at all cell site receivers at which it is received. A channel of a cell is then assigned for the call based on the signal strengths of the signals received at the cell site receivers, with preference given to the cell at which the strongest signal is received. Such a method is described in U.S. Pat. No. 4,144,412, entitled "Method of assigning a radio channel to a calling mobile body of mobile communication system and radio channel assigning system therefor," issued on Mar. 13, 1979 to Ito et al.
While this method achieves adequate results, it is not optimum because the propagation characteristics of the inbound frequency of the control channel typically do not closely represent significant propagation characteristics of the outbound frequency of the channel selected by this method, such as interference from noise, interference from co-channel signals received by the cellular unit from other groups, and Rayleigh fading dependent signal strength, and therefore the best channel is not always chosen.
For new generation radio communication systems, achieving maximum capacity is essential to success. In such systems, a selection of one of multiple transmission modes can be used to optimize throughput between a base station and a cellular unit. A description of such a system is given in U.S. Pat. No. 5,546,411, entitled "Method and Apparatus for Adaptively Selecting a Communication Strategy in a Selective Call Radio Communication System," issued on Aug. 13, 1998 to Leitch et al. While this method achieves improvements over prior art systems, it does not provide criteria for choosing a transmission channel, and does not address methods of controlling interference.
Thus, what is needed is a method that optimizes the selection of link setup parameters for use in transmitting outbound and inbound messages on a narrowband link in a cellular radio system.